In recent years, a cellular phone has spread widely as one of mobile communication devices, and the multifunctionality has been required for the mobile devices. For example, in a semiconductor integrated circuit device used in the cellular phone, the demand for low power consumption has been extremely strong.
As the technology for low power consumption in this kind of semiconductor integrated circuit device, for example, one technology where a core power source area is divided, and ON and OFF of the power source is controlled for each of the divided areas is known.
According to the examinations by the inventors of the present invention, in the ON/OFF control of the power source, there is the one which supports the two modes of R-standby mode and U-standby mode.
The R-standby mode is an operation mode where power supply to all areas (function modules) other than a built-in RAM (Random Access Memory) and a backup module which resets the contents of a part of registers to the state before power shutdown after recovery of power supply is turned OFF, and thus a quick state recovery is possible by external interruption.
At the time of this R-standby mode, the built-in RAM is controlled to be in a Resume mode (low leakage current state where contents can be retained and access is prohibited).
Meanwhile, the U-standby mode is an operation mode where power supply to all the areas other than an I/O (Input/Output) circuit and a power supply control circuit is turned OFF, and a power-on reset state is kept after recovery of power supply.